David Cameron, the British prime minister, allowed his former spokesman, Andrew Coulson, access to some of the government's most sensitive secrets without full security clearance, an inquiry has been told.

Asked on Thursday by Robert Jay, the lead lawyer for judge Brian Leveson, who heads the inquiry, whether he had any unsupervised access to information designated top secret, Coulson, former editor of the News of the World, said: "I may have done, yes."

"Did you ever attend meetings of the national security council?" Jay asked about a body of senior politicians, defence and intelligence chiefs which is chaired by the prime minister.

"Yes," Coulson said.

The Leveson inquiry heard that Coulson had been asked few questions by Cameron's Conservative Party about his past and that the party did not carry out full security checks.

A full security clearance procedure includes a review of the applicant's finances and detailed interviews about their past.

Unethical practices

The inquiry was set up by the government to look into press standards following allegations of phone hacking at the News of the World.

The Sunday paper was shut down by News International, its London-based parent company, amid a firestorm over its journalists' unethical practices.

Coulson, who left the News of the World after the jailing of one of his reporters for phone hacking, was hired by the Conservative party, helping steer Cameron's bid to become prime minister.

Critics say Cameron appointed Coulson in order to secure the backing of Rupert Murdoch, the media baron whose newspapers have been courted by British politicians to secure endorsement during elections.

But Coulson denied there was a deal between the party and Murdoch's papers.

"I want to make it quite clear that there was never any inappropriate deal between the papers and the party," Coulson said.

"There were no conditions or contingencies suggested or levied in return for a newspapers' support."

The appointment showed a lack of judgement, critics said.

Shares in News Corp

Coulson told the hearing that he had owned shares in Murdoch's News Corp while he worked for Cameron, an issue he said could raise the potential for a perception of a conflict of interest.

He denied any "grand conspiracy" between media tycoons and senior politicians but did say that the fallout from the phone hacking scandal was forcing politicians to distance themselves from journalists and media bosses.

Thursday's developments follow a critical British parliamentary report last week that said Murdoch was unfit to lead a major global company.

British legislators said in the report that Murdoch had been guilty of "wilful blindness" over the News of the World hacking scandal.

The involvement of Coulson and another former editor - Cameron's friend Rebekah Brooks - turned hacking story into a huge scandal, with ties between senior politicians, the police and the media coming under close scrutiny.

The Guardian newspaper, which broke the phone-hacking scandal, has said it warned Cameron against employing Coulson, citing information it had but was unable to publish for legal reasons.